The hypothesis that motivates the Children's Hospital, Boston, Learning Disabilities Research Center (LDRC) is that neurodevelopmental mechanisms supporting temporal information processing are specifically disordered in learning disabled children. The basic approach to investigating this hypothesis is to use a variety of psychophysical, neuropsychological, and neurophysiological probes with children classified as LD and to compare the results of such probes with a normative sample, and, more particularly, among the LD children themselves. It is the belief of the LDRC that data from these measures will permit the subgrouping of LD children in a way that is more reflective of different underlying neurophysiological deficits that, via various mechanisms, lead to the diagnosis of LD. One of the most powerful tools now available for doing non-invasive neurophysiological research with humans is functional Magnetic Resonance Imaging (fMRI). Project V will apply this technology to the study of the various subgroups of LD and non-LD children supplied and characterized by Projects I-IV. The initial purpose of Project V is to examine the activity of children's brains as they are performing the tasks of Project I. The goal is to seek underlying neurophysiological distinctions that will reflect the subgroupings proposed from Project I. As the program continues, tasks from Projects III and IV will also be adapted to the context of fMRI. Specifically, this project will: develop techniques for obtaining high quality functional Magnetic Resonance Imaging (fMRI) data from children; adapt the testing procedures proposed in Project I (low level information processing (LLIP)), Project III (neurobehavioral assessment), and Project IV (EEG), to the environment of fMRI; develop fMRI procedures to enhance MR's effective spatial and temporal resolution in the context of presenting the LLIP tasks of Project I to children; use fMRI to examine brain function of a substantial subset of the subject pool using tasks from Projects I, llI, and IV as adapted to fMRI; test proposed subgroups of LD subjects as derived by Projects I-IV; and seek such subgroups based on the fMRI data itself.